Artificial Life in computer. Including evolution of course...! Original idea by Tom Ray. With simple assembler language, you can make Tierra program (called gene or genome) that copy itself and start evolution by mutations.
Tom Ray has written lot of texts about artificial life, evolution and genetic algorithms. Just search the internet for more complete information of Tierra.
My implementation of Tierra is fully character based and it uses only standard C++ input (cin) and output (cout, printf) functions. So I think it's quite portable.
Basic operation of Tierra program:
At start, program just copy itself repeatedly. You can check this first tierra program from source code section below.
1. Calculate needed memory block (own size, this is calculated only
at first copy).
2. Allocate enough memory for child process
3. Copy own code to allocated memory
4. Ask operating system to start child
5. Goto 2.
TierraCPU is virtual multitasking CPU. It has few registers, which are accessible with Tierra Assembler opcodes.
int ax; // address register
int bx; // address register
int cx; // numerical register
int dx; // numerical register
int sp; // stack pointer
int stack; // stack
int ip; // instruction pointer
Assembler commands fits in one byte (actually in 5 bits)
|or1||flip low order bit of cx, cx^=1|
|shl||shift left cx, cx<<=1|
|zero||set cx to zero, cx=0|
|if_cz||if cx==0 execute next intruction|
|sub_ab||substract bx from ax,result to cx, cx=ax-bx|
|sub_ac||substract cx from ax, ax=ax-cx|
|inc_a||increment ax, ax++|
|inc_b||increment bx, bx++|
|dec_c||decrement cx, cx--|
|inc_c||increment cx, cx++|
|push_ax||push ax on stack|
|push_bx||push bx on stack|
|push_cx||push cx on stack|
|push_dx||push dx on stack|
|pop_ax||pop to ax|
|pop_bx||pop to bx|
|pop_cx||pop to cx|
|pop_dx||pop to dx|
|call||call subroutine (nearest)|
|ret||return from subroutine|
|mov_cd||move cx to dx, dx=cx|
|mov_ab||move ax to bx, bx=ax|
|mov_iab||move instruction at [bx] to [ax], [ax]=[bx]|
|adr||search template (nearest) address to ax|
|adrb||search template (backward) address to ax|
|adrf||search template (forward) address to ax|
|mal||allocate memory, cx=size, return address in ax|
|divide||cell division, start of cell in ax|
Assembler (t_asm) and disassembler (t_dasm):
These tools use stdin for input and stdout as output. So it is nice to redirect those to file.
Usage: t_asm <input-file >output-file
t_asm compiles assembler commads (ascii file) to bytecodes (binary file). t_dasm compiles bytecodes back to assembler listing. Assembler listing is commented with those descriptions above.
Source for Tierra <tierra.tgz> (15k)
Here is sample Tierra program <80aaa.asm> (3k)
Statics file from one run of Tierra <statics.csv> (8k)
ELF executables <tierra-linux-elf.tgz> (150k)
Screenshot at Tierra startup. Program takes filenames as parameters. Those bytecode files are loaded to virtual memory in given order and system is prepared to run.
[korma@localhost ajo1]$ ../tierra ../80aaa
cycles left: 31
-----General System screen-----
CPU current/all 1/1
cycles this/all 1/1 (0 M)
free memory 255920 bytes in 1 blocks
used memory 80 (0 %)
0 bit flips, 0 invalid instructions, 0 killed CPUs
Different genomes 0
free_mem=0k, cpu_queue=0k, gene_store=0k, temp_store=0k
start=0 size=80 (0,0)
ax=0 bx=0 cx=0 dx=0
ip=1 sp=0 flag=0
stack: 0 0 0 0 0 0 0 0 0 0
[ 0] 0: nop_1
[ 1]-> 1: nop_1
[ 2] 2: nop_1
[ 3] 3: nop_1
[ 4] 4: zero
[ 5] 5: or1
"General System screen" section shows information about system, memory
"registers" section shows registers for currently running process.
"Next opcodes" shows opcodes at instruction pointer
The control keys are:
command (h=help): h
d - step 1 instruction
s # - step # instructions
w # - write to disk all genes at size #
g - print genebank
m - print memory info
e - print error info
t - toggle error counting
c - print cpu table
h - print keys
q - quit
This command run 300 000 instructions with Tierra system. After that the General System screen is printed again.
When running, new genomes (evolved programs) are written to file in current directory. Filename is made up of genome size and counter number. Example "43_157" means that size is 43 opcodes and that was 157th written genome.
Tierra writes some statics about The Life to file (statics.csv, check source code section). This file is easy to view in StarCalc or other Spreadsheet program (MS Excel is suitable, if you don't have any better) as Comma Separated Values. This makes it easy to draw charts about life.
markku (dot) t (dot) korsumaki (at) mbnet (dot) fi
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